Crystal holder



G. L. USSELMAN ET AL 2,193,501

March 12, 1940.

CRYSTAL HOLDER Filed Nov. 16, 1937 s USSELMAN AND ENTOR a? as it. BY fEFNKL/N 7 n/(nH/L,

ATI'OR EY.

Patented Mar. 12, 1940 UNITED STATES PATENT OFFICE f CRYSTAL HOLDER wareApplication November 16, 1937, Serial No. 174,768

llclaims.

This invention relates to a novel and improved piezo-electric crystalholder and deals more specifically with the insulation and spacing ofthe electrodes in a crystal housing having a fixed I air gap between thecrystal and the electrodes.

An object of this invention is to simplify and improve piezo-electriccrystal holders to reduce the cost and maintenance thereof.

Another object of this invention is to provide a piezo-electric crystalholder in which the insulation and spacing material for the electrodesis so chosen as to have substantially the same coefficient of linearexpansion as the average value of the crystalline quartz element.

A feature of this invention is the use of a multi-electrodeholdercomprising a single crystal and at least four electrodes, which holderis particularly useful in a push-pull circuit.

Another feature of this invention is that the insulation, electrodes andspacers determining the air gap are so chosen as to give the leastchange in gap capacity ofthe crystal holder for a given change in holdertemperature.

Piezo-electric crystals are generally old'in the art; however, therecent trend in the piezo-electric crystal art has been toward crystalswith a low or zero temperature coefficient of frequency; by the use ofsuch crystals, temperature control devices are either eliminated orreduced to poor temperature control thus materially reducing the cost.in crystal holders of the fixed gap type, one of the reasons forchanging frequency with changing temperature is the change in the gapcapacity due to unequal expansion or contraction of the quartz,electrodes, insulation and spacing member.

Crystal holders known in the prior art are usually made with suchmaterial as porcelain or Bakelite insulation and electrodes of brass orcopper; for the material in this invention, nickel or Monel metalelectrodes are preferably used as these metals have a coefficient ofexpansion very close to the crystalline quartz crystal. Also, for theinsulation material, we prefer to use glass insulation having acharacteristic similar to that of quartz; therefore, the insulatingspacers of this improved crystal holder are preferahlymade of glass orfused quartz, depending upon the characteristics desired. a

The present invention may'best be unders and described by referring tothe accompanying drawing, in which:

Fig. 1 is a side elevation of an improved crystal holder having glassend support members;

Fig. 1a is an end view of Fig. 1;

Fig. 1b is a detail section showing the method of supporting theelectrodes to the glass end support members;

Fig. 2 is a side view of a crystal holder having insulating supportplates upon which the crystal and electrodes are supported;

Fig. 2a is an end view of Fig. 2;

Fig. 3 is a front view of another modification similar to that of Fig.1; and

Fig. 3a is an end view of Fig. 3.

Referring now in detail to Fig. lof the drawing, four metal electrodes#1, 2, 3 and 4 are shown which are made of Monel or nickel metal whichhas substantially the same similar coefficient of expansion as that ofthe quartz; or, they may be made of some other metal with a slightlydifferent coefficient of expansion, which will give a desired expansioncharacteristic. The electrodes are supported by glass end supportmembers S, i, I and 8 which are arranged to give the proper air gap, forthe crystal in use, and are also cut to allow a minimum motion of thequartz crystal 9 while it is in operation. A single piece copper shieldI is attached to the insulating end members by means of terminals I Iand binding screws If; this shield is particularly desirable forshielding between grid and plate electrodes of certain crystal circuits.In order to keep the air gap constant, the metallic members not employedas electrodes are kept to a minimum; therefore, the electrode bindingscrews l3 and H are also employed to make the electrical connections bybeing fastened to lugs l5, l6, l1 and I8.

The lower portions of electrodes I, 2, 3 and 4 are fastened by means ofscrews l9, as shown in Fig. 1b. The adjacent screws are countersunk to asufficient depth to prevent short circuiting between the two electrodes.The lower insulating support members I and 8 are provided withprojections II and 2| to keep the crystal from slipping out of place.The overhanging portion of copper shield I! may, if desired, be used forattaching the holder to any suitable support (not shown). 7

Fig. 2 shows a pair of'insulating support plates ll and 3| upon whichfour metallic electrodes 32, 33, 34 and 3! are'mounted. A piano-electriccrystal 3' is spaced from the electrodes by means of four glass orquartz tube spacing members 31, which like the end supports 5, 6, 1. and8 are arranged to give the proper air gap for the crystal in use, andalso are cut with a groove to allow a minimum motion of the quartzcrystal 9 while it is in operation. The plates and 3| are spaced bymembers 31 and bound together by means of four screws 38 and nuts 39.The electrodes are symmetrically arranged upon insulating plates 30 and3| by means of a plurality of screws 40. In order to keep the amount ofmetal to a minimum, electrical connections are made to the electrodes bymeans of soldering lead wires l B, into the apertures 42.

Fig. 3 is a modification similar to that of Fig. 1, except that itcombines certain of the features of Fig. 2 in that the crystal spacingbetween the electrodes is maintained by means of spacing tubes 50, oneof which is provided to space apart the top end support members 5| and52 and three spacing members 50 are provided for the lower end supports53 and 54, the electrodes 55, 56, 51 and 58 being secured to end members5| to 54, inclusive, by means of a plurality of screws 59. Theelectrical connections are made similar to that of Fig. 2 in that a lead60 is soldered in the end portion of the electrodes.-

Figs. 2 and 3 show other suggested variations from those of Fig. -1 toallow greater freedom in selection of materials for the characteristicsdesired.

Figs. 1 and 3 show types in which there is no plane of symmetry of theelectrodes perpendicular to the plane of the crystal which shows thetype in which the electrodes are symmetrically arranged, and while onlythree modifications of .this invention are shown, it is to be distinctlyunderstood that it is capable of taking other forms.

What is claimed is:

1. A piezo-electric crystal holder having an air gap comprising apiezo-electric' crystal, insulating members located at the ends of saidcrystal, and metallic electrodes adjacent each face of said crystalandsecured to said insulating members.

2. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, a pair of insulating members located at one endof said crystal, and two metallic electrode members located at each faceof said crystal, said metallic end members being secured to saidinsulating members.

3. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, a pair of insulating members located at one endof said crystal, and two metallic electrode members located at each faceof said crystal, said metallic end members being secured to saidinsulating members, the area of said electrodes being substantially lessthan the area of said crystal.

4. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, a pair of insulating members located at one endof said crystal, and two metallic electrode members located at each faceof said crystal, said metallic end members being secured to saidinsulating members, the area of said electrodes being substantially lessthan the area of said crystal, and a metallic shield located betweensaid electrodes.

5. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, glass spacing members located at the ends ofsaid crystal, and metallic electrodes adjacent each face of said crystaland secured to said spacing members.

6. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, a plate of insulating material of greater areathan said crystal for supporting and spacing said crystal, and metallicelectrodes adjacent each face of said crystal and secured to saidinsulating plate.

'7. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, a plate of insulating material of greater areathan said crystal for supporting and spacing said crystal, and twometallic electrodes adjacent each face of said crystal and secured tosaid insulating plate.

8. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, a plate of insulating material of greater areathan said crystal for supporting and spacing said crystal, andunsymmetrically arranged metallic electrodes adjacenteach face of saidcrystal and secured to said insulating plate.

9. A piezo-electric crystal holder having an air gap, comprising aquartz piezo-electric crystal, insulating material for supporting andspacing said crystal, metallic electrodes adjacent each face of saidcrystal and secured to said insulating material, the material of saidinsulation and said metallic electrodes being so chosen. so as to havean expansion characteristic similar to said quartz piezo-electriccrystal to give a minimum change in gap capacity for a definite changein the crystal holder temperature.

10. A piezo-electric crystal holder having a, fixed air gap comprising apiezo-electric crystal, a pair of insulating plates having a greaterarea than said crystal for supporting said crystal, a plurality ofmetallic electrodes adjacent each face of said crystal and secured tosaid insulating plates, a plurality of insulating tubes interposedbetween said pair of insulating plates for spacing said crystal fromsaid electrodes, and binding means for securing said insulating platesand tubes together.

11. A piezo-electric crystal holder having a fixed air gap comprising apiezo-electric crystal, a pair of insulating plates having a greaterarea than said crystal for supporting said crystal, two metallicelectrodes adjacent each face of said crystal and secured to saidinsulating plates, a plurality of glass tubes interposed between saidpair of insulating plates for spacing said crystal from said insulatingplates and tubes together.

GEORGE L. USSELMAN. RALPH E. FRANKLIN.

